Aerobic exercise is a popular form of exercise that improves one's cardiovascular health by reducing blood pressure and providing other benefits to the human body. Aerobic exercise generally involves low intensity physical exertion over a long duration of time. Typically, the human body can adequately supply enough oxygen to meet the body's demands at the intensity levels involved with aerobic exercise. Popular forms of aerobic exercise include running, jogging, swimming, and cycling, among other activities. In contrast, anaerobic exercise typically involves high intensity exercises over a short duration of time. Popular forms of anaerobic exercise include strength training and short distance running.
Many people choose to perform aerobic exercises indoors, such as in a gym or in their home. Often, a user will use an aerobic exercise machine to perform an aerobic workout indoors. One type of aerobic exercise machine is a treadmill, which is a machine that has a running deck attached to a support frame. The running deck can support the weight of a person using the machine. The running deck incorporates a conveyor belt that is driven by a motor. A user can run or walk in place on the conveyor belt by running or walking at the conveyor belt's speed. The speed and other operations of the treadmill are generally controlled through a control module that is also attached to the support frame and within convenient reach of the user. The control module can include a display, buttons for increasing or decreasing a speed of the conveyor belt, controls for adjusting a tilt angle of the running deck, or other controls. Other popular exercise machines that allow a user to perform aerobic exercises indoors include elliptical trainers, rowing machines, stepper machines, and stationary bikes, to name a few.
One type of treadmill is disclosed in U.S. Pat. No. 6,042,513 issued to John Koteles, et al. In this reference, a runaway protection mechanism is provided for use in, for example, an exercise treadmill for driving its moving treadmill belt. According to Koteles, an electric motor is connected to an electric power source, such as an alternating-current wall outlet. The runaway protection mechanism includes a disconnect mechanism for disconnecting the motor from the electric power source and thereby de-energizing the motor during a runaway condition. The runaway protection mechanism further includes a safety mechanism for comparing the actual motor speed with a desired motor speed and activating the disconnect mechanism when the actual speed exceeds the desired speed by a predetermined amount.